I very recently downloaded the Montserrat font, not knowing that it was already in the fonts list. This resulted in a duplicate of that font showing up in the dropdown.
Problems I experience with this includes slight clutter in the font face dropdown, as well as the font face dropdown thinking the duplicate font is a different font, even though both instances use the same font face, albeit the different one (see below images).
Both selected (notice how it should display Montserrat, but instead displays nothing):
First Montserrat selected:
Second Montserrat selected:
I have tried searching for an uninstall button, as well as research this on the forum, even running through a filtered advanced Google search. Unfortunately, all I came across is a (unhelpfully short) post stating that you are unable to delete downloaded fonts for some reason.
Again, this is a minor issue, but deletion of fonts should be possible, or at least easy to find.